Fatty acid alkyl esters are widely used products. Most of them are used as renewable transport fuel named “biodiesel”. Production of fatty acid iso-propyl esters mainly based on acid process, but using of alkaline catalysts may give good yields also. Alkaline catalysts have some advantageous such as low corrosivity and higher reaction rate. In current work the effectivity of potassium hydroxide and treated potassium hydroxide solution as catalyst for transesterification was compared. It was shown that using of KOH solution in iso-propyl alcohol after special treatment gives almost twice higher yields (95-96 %) from refined sunflower oil triglycerides than over KOH under the same conditions. Yield of fatty acids iso-propyl esters from wasted frying oil stabilized after 1-1.5 hours of reaction over both catalysts. Using 1.8 and 2.0 % treated catalyst at 90 °C leads to yield of about 86-88 % at 9:1 alcohol-to-oil ratio. Reaction temperature has significant impact on a yield wich decreases with temperature reduce in the range from 30 to 90 °C. During reaction proceeding the alkali saponification and thus loss the catalytic activity, which displayed in stopping the yield rising. The lower yield of esters from wasted oil comparing to the refined oil may be caused by presence of heavy polymerized triglycerides components formed during frying. Such components cannot be fully converted into monoalkylesters and gives also the oligomerized esters, which is not visible in standard gas chromatographic analysis of biodiesel. Indirect confirmation of the presence of such compounds in wasted frying oil sample is the sufficiently larger mass of the cube residue in vacuum distillation. For refined oil amount of such residue was only 5.4 %, while for wasted oil it was three time higher (14.9 %). In case of wasted frying oil as raw stuff, even after full conversion and effective self-separation conventional purification methods (like water washing or dry washing with adsorbents) may not provide the necessary purity of resulted biodiesel due to the presence of heavy oligomeric admixtures. In such cases vacuum distillation should be included as necessary final purification stage.
The Biodiesel Handbook, 2nd edn. (G. Knothe, J. Krahl, J. van Gerpen). Elsevier, Urbana, Illinois, 2010. 482.
Malins K., Kampars V., Kampare R., Prilucka L., Brinks J., Murnieks R., Apseniece L. Properties of rapeseed oil fatty acid alkyl esters derived from different alcohols. Fuel. 2014. 137. 28-35.
Wang W., Li F., Li Y. Effect of biodiesel ester structure optimization on low temperature performance and oxidation stability. J. Mater. Res. Technol. 2020. 9 (3). 2727-2736.
Kleinová A., Paligováa J., Vrbová M., Mikulec J., Cvengroš J. Cold flow properties of fatty esters. Trans IChemE, Part B, Process Safety and Environmental Protection. 2007. 85 (B5). 390-395.
Dunn R.O. Cold-flow properties of soybean oil fatty acid monoalkyl ester admixtures. Energy Fuels. 2009. 23. 4082-4091.
Silva L.N., Cardoso C.C., Pasa V.M.D. Synthesis and characterization of esters from different alcohols using Macauba almond oil to substitute diesel oil and jet fuel. Fuel. 2016. 166. 453-460.
Wang P.S., Tat M.E., Gerpen V. The production of fatty acid isopropyl esters and their use as a diesel engine fuel. J. Am. Oil Chem. Soc. 2005. 82. 845-849.
Sanli H., Canakci M. Effects of different alcohol and catalyst usage on biodiesel production from different vegetable oils. Energy Fuels. 2008. 22. 2713-2719.
Hanh H.D., Dong N.T., Okitsu K., Nishimura R., Maeda Y. Biodiesel production through transesterification of triolein with various alcohols in an ultrasonic field. Renew. Energy. 2009. 34. 766-768.
Sánchez M., Bergamin F., Peña E., Martinez M., Aracil J. A comparative study of the production of esters from Jatroha oil using different short-chain alcohols: Optimization and characterization. Fuel. 2015. 143. 183-188.
Likozar B., Levec J. Transesterification of canola, palm, peanut, soybean and sunflower oil with methanol, ethanol, isopropanol, butanol and tert-butanol to biodiesel: Modelling of chemical equilibrium, reaction kinetics and mass transfer based on fatty acid composition. Appl. Energy. 2014. 123. 108-120.
Becker H. Introduction to the electronic theory of organic reactions; “Mir”: Moscow, 1977. 658. (In Russian) 13. Hájek M., Skopal F., Vávra A., Kocík J. Transesterification of rapeseed oil by butanol and separation of butyl ester. J. Cleen. Prod. 2017. 155 (Part 1). 28-33.
Patent UA123473 C2. Zubenko S.O., Konovalov S.V., Patrylak L.K. Method of preparing catalyst for fatty acid esters production. Ukraine. 2021. (In Ukrainian)
Zubenko S.O. The simple method of vegetable oils and oleochemical products acid value determination. Catalysis and Petrochemistry. 2021. N31. 69-74.
Thoai D.N., Tongurai C., Prasertsit K., Kumar A. A novel two-step transesterification process catalyzed by homogeneous base catalyst in the first step and heterogeneous acid catalyst in the second step. Fuel Proc. Technol. 2017. 168. 97-104.
Patrylak L.K., Zubenko S.O., Konovalov S.V., Povazhnyi V.A. Alkaline transesterification of sunflower oil triglycerides by butanol-1 over potassium hydroxide and alkoxides catalysts. Issues of chemistry and chemical technology. 2019. 5. 93-103.
Konovalov S., Patrylak L., Zubenko S., Okhrimenko M., Yakovenko A., Levterov A., Avramenko A. Alkali synthesis of fatty acid butyl and ethyl esters and comparative bench motor testing of blended fuels on their basis. Chem. Chem. Technol. 2021. 15 (1). 105-117.
Brunschwig C., Moussavou W., Blin J. Use of bioethanol for biodiesel production. Prog. Energ. Combust. 2012. 38 (2). 283-301.
Balat M., Balat H. Progress in biodiesel processing. Appl. Energy. 2010. 87. 1815-1835.
Demirbas A. Progress and recent trends in biodiesel fuels. Energy Convers. Manag. 2009. 50. 14-34.
Murugesan A., Umarani C., Chinnusamy T.R., Krishnan M., Subramanian R., Neduzchezhain N. Production and analysis of bio-diesel from non-edible oils-a review. Renew. Sustain. Energy Rev. 2009. 13. 825-834.
Ejikeme P.M., Anyaogu I.D., Ejikeme C.L., Nwafor N.P., Egbuonu C.A.C., Ukogu R., Ibeesi J.A. Catalysis in Biodiesel Production by Transesterification Processes-An Insight E- J. Chem. 2010. 7. 1120-1132.
Ruiz-Méndez M.V., Marmesat S., Liotta A., Dobarganes M.C. Analysis of used frying fats for the production of biodiesel. GRASAS ACEITES. 2008. 59. 45-50.
Vieitez I., Callejas N., Irigaray B., Pinchak Y., Merlinski N., Jachmanian I. Grompone M. Acid value, polar compounds and polymers as determinants of the efficient conversion of waste frying oils to biodiesel. J. Am. Oil Chem. Soc. 2014. 91. 655-664.